Before you pain at the sight of another "trailer light problem" give me the curtousey of a read. It's not a typical fuse blown problem.

I just installed a flatbed on my 2003 2500hd farm truck. I wired the lights to the trailer tail of my underbed harness (as my flatbed is 2 wire tail and factory harness on the frame is 3). Ive been told by numerous country boys/installers this is the way to do it, so I oblige.

I wire it up, turn it on, and all is well with the lights except for my right rear blinker/brake light and my reverse lights.

I go to the fuse box under hood, and in cab by driver side and check all the fuses. No problems there.

I think it could be my flat bed electrical, so I swap some wires and they blink, brake, and the back ups turn on. Son of a...

Grab my multimeter, pull the trailer light fuses, and there's no 12v at my back up fuse, or right brake/turn signal.

I then checked every fuse in both boxes to make sure I'm not an idiot. No blown fuses anywhere to be found.

I start reading online, and think that perhaps my hazard flasher (giant 10 pin under steering column above parking brake) is broken. Bought a new one, install it, and still the same effing problem.

Now I'm trying to figure out what's going on, and I need your help. What can I check/verify next? As mentioned, I have a multimeter and just about anything else I might need to check electrical.